A screen device of the type mentioned is known for example from EP 1 570 919 B1. This screen device comprises a roller screen comprising interlocking helical or spiral rollers which are arranged, such that they can be rotary-driven, next to each other. A screening material introduced onto the roller screen is separated into a fine grain fraction which falls down between said screen rollers, a first oversize grain fraction which is conveyed on the screen rollers transverse to the axial direction of the rollers, and a second oversize grain fraction which is conveyed in the axial direction of the rollers by the screw action of the screen rollers. The first oversize grain fraction is discharged transverse to the axial direction of the rollers at one end of the roller screen. The screen rollers are mounted at one end only and therefore overhung, such that the second oversize grain fraction can be discharged without hindrance at the freely projecting end of the screen rollers.
EP 2 329 891 B1 describes another example of a screen device. Instead of helical or spiral rollers, the screen device comprises screen rollers comprising screen discs which are arranged in parallel next to each other in the axial direction of the rollers and together form a disc screen. In order to still convey some of the oversize grain fraction in the axial direction of the rollers, the screen rollers of the disc screen are arranged such that the roller axes are inclined obliquely downwards from an introducing region of the disc screen towards an output region. The relevant oversize grain fraction is therefore conveyed in the axial direction of the rollers by gravity. Unlike the first screen device mentioned, the screen rollers of the disc screen are mounted on both sides, such that measures have to be taken so as not to excessively obstruct the removal of the relevant oversize grain fraction past the axial ends of the screen rollers.